Both low and high molecular weight azomethine polymers (commonly termed Schiff-base polymers) have been described in literature and various patents. Generally, these azomethine polymers are made by reacting aromatic dialdehydes with aromatic diamines. The preparation of low molecular weight polyazomethines by solution polymerization has been described by Delman et al in Marcromol Sci. Chem. Al. (1) 147-148 (67). U.S. Pat. Nos. 3,516,0970, 3,516,971 and 3,526,611 describe the synthesis by melt polymerization of high molecular weight Schiff-base polymers. The high molecular weight azomethine polymers are taught as being highly insulating and thermally stable, i.e., capable of withstanding high temperatures for sustained periods of time without undergoing significant degradation or phase change. They have thus been suggested for aerospace applications requiring polymers having high temperature stability. While the carboxy terminated azomethines of this invention are of relatively low molecular weight, we have found that they have good thermal stability and high melting points.
It is known in the art that carboxy functional materials may be reacted with epoxy resins to form thermoplastic and thermoset materials. We have now found that the carboxy terminated aromatic azomethines of this invention, when reacted with epoxy resins, produce polyester materials with high glass transition temperatures. Such high glass transition temperature polyesters would be useful in applications requiring materials having good thermal stability and relatively high melting points.